System and method of manufacturing composite core

ABSTRACT

A method of manufacturing a composite core can include: wrapping a mandrel in a mandrel wrapping process by securing a mandrel with a winding jig; orienting the composite material at a wrap angle to the mandrel; and depositing the composite material around a circumference of the mandrel. The method can further include assembling the wrapped mandrels in a tool and applying a pressure to the composite material during a curing cycle.

BACKGROUND

1. Technical Field

The present disclosure relates to a system and method of manufacturingcomposite core.

2. Description of Related Art

A composite structure, such as a composite honeycomb core, canconventionally be manufactured using a manual process of creating acorrugated pattern in a plurality of composite layers by pressingmandrels against the composite layers. For example, the method describedin U.S. Pat. No. 5,567,500, utilizes such a process. The geometry ofadjacent composite layers to collectively form the cells of thehoneycomb core. Such a process is labor intensive which can make thehoneycomb core product very expensive. Further, this manufacturingmethod can result honeycomb core that is not optimal for variousstructural implementations.

Hence, there is a need for an improved system and method formanufacturing composite core.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the system and method ofthe present disclosure are set forth in the appended claims. However,the system and method itself, as well as a preferred mode of use, andfurther objectives and advantages thereof, will best be understood byreference to the following detailed description when read in conjunctionwith the accompanying drawings, wherein:

FIG. 1 is a side view of an rotorcraft, according to one exampleembodiment;

FIG. 2 is a side view of a panel, according to one example embodiment;

FIG. 3 is a cross-sectional view of the panel, taken from section lines3-3 in FIG. 2, according to one example embodiment;

FIG. 4 is a perspective view of a composite core, according to oneexample embodiment;

FIG. 5 is a cross-sectional view of the composite core, taken fromsection lines 5-5 in FIG. 4, according to one example embodiment;

FIG. 6 is a schematic view of a method of manufacturing a compositecore, according to one example embodiment;

FIG. 7 is a partially stylized view of a system for wrapping andassembling mandrels, according to example embodiment;

FIG. 8 is an exploded view of a mandrel winding jig, according toexample embodiment;

FIG. 9A is a top view of a winding jig, according to example embodiment;

FIG. 9B is a top view of a winding jig, according to example embodiment;

FIG. 10 is a top view of a winding jig, according to example embodiment;

FIG. 11 is a top view of a winding jig, according to example embodiment;

FIG. 12 is a stylized, plan view of a mandrel being wrapped with uncuredcomposite material, according to one particular embodiment;

FIG. 13 is a stylized, plan view of a mandrel being wrapped with uncuredcomposite material, according to one particular embodiment;

FIG. 14 is a top view of a winding jig, according to example embodiment;

FIG. 15 is a detail view taken from FIG. 14, according to one exampleembodiment;

FIG. 16 is a detail view taken from FIG. 14, according to one exampleembodiment;

FIG. 17 is a perspective view of a cutting tool, according to oneexample embodiment;

FIG. 18 is a is an end view of a plurality of composite-wrapped mandrelsstacked on a partial tool, according to one example embodiment;

FIG. 19 is an end view of a plurality of composite-wrapped mandrelsassembled in a tool, according to one example embodiment;

FIG. 20 is a plan view of a plurality of composite-wrapped mandrelsassembled in a tool, according to one example embodiment; and

FIG. 21 is a cross-section view of a mandrel taken from FIG. 8,according to one example embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the system and method of the presentdisclosure are described below. In the interest of clarity, all featuresof an actual implementation may not be described in this specification.It will of course be appreciated that in the development of any suchactual embodiment, numerous implementation-specific decisions must bemade to achieve the developer's specific goals, such as compliance withsystem-related and business-related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time-consuming but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present disclosure, the devices,members, apparatuses, etc. described herein may be positioned in anydesired orientation. Thus, the use of terms such as “above,” “below,”“upper,” “lower,” or other like terms to describe a spatial relationshipbetween various components or to describe the spatial orientation ofaspects of such components should be understood to describe a relativerelationship between the components or a spatial orientation of aspectsof such components, respectively, as the device described herein may beoriented in any desired direction.

Referring now to FIG. 1 in the drawings, a rotorcraft 101 isillustrated. Rotorcraft 101 has a rotor system 103 with a plurality ofrotor blades 105. The pitch of each rotor blade 105 can be managed inorder to selectively control direction, thrust, and lift of rotorcraft101. Rotorcraft 101 can further include a fuselage 107, anti-torquesystem 109, and an empennage 111.

Rotorcraft 101 is merely illustrative of the wide variety of aircraft,vehicles, and other objects that are particularly well suited to takeadvantage of the method and system of the present disclosure. It shouldbe appreciated that other aircraft can also utilize the method andsystem of the present disclosure. Further, other vehicles and objectscan utilize composite core manufactured by the system and method of thepresent disclosure. Illustrative embodiments can include wind turbineblades, sea based vehicles, radomes, enclosures, shelters, bridge decks,building facades, ground vehicles, rail vehicles, air vehicles, spacevehicles, and manned or un-manned vehicles, to name a few.

Referring now also to FIGS. 2 and 3, a panel 113 on rotorcraft 101 isillustrative of a wide variety of structures that can include a coremember configured as a lightweight means of generating strength andstiffness in the structure. Panel 113 is a composite assembly that caninclude an upper skin 301, a lower skin 303, and a composite core 305.Composite core 305 can be adhesively bonded to upper skin 301 and lowerskin 303. It should be appreciated that panel 113 can take on a widevariety of contours and configurations.

Referring now also to FIGS. 4 and 5, composite core 401 is illustratedin a raw stock configuration. Composite core 305 (shown in FIG. 3),having implementation specific geometry, can be carved from compositecore 401, for example. In another embodiment, composite core 401 ismanufactured in a net shape such that a subsequent carving procedure isnot required. Composite core 401 can be of a wide variety of materialsand cell sizes. For example, in one embodiment composite core 401 ismade from a carbon fiber and resin composite system. Composite core 401includes a plurality of tubes 403 (only one tube labeled for clarity)arranged in a two-dimensional array. However, in one embodiment thetubes 403 can be selectively positioned such that the end portions arenot in the same plane. Each tube 403 defines a passageway or “cell” 405extending therethrough. Composite core 401 can comprise any suitablenumber, size, cross-sectional shape, and construction of tubes 403.

Each tube 403 of composite core 401 can include a plurality ofreinforcement fibers disposed in a polymeric matrix. For example, tubes403 may comprise fibers comprising one or more of carbon, graphite,glass, an aromatic polyamide (i.e., “aramid”) material, a variant of anaromatic polyamide material (e.g., a polyparaphenylene terephthalamidematerial, such as Kevlar® by E. I. du Pont de Nemours and Company ofRichmond, Va.), or the like. The scope of the present disclosure,however, encompasses fibers comprising any suitable material orcombination of materials. The polymeric matrix may comprise any suitableresin system, such as a thermoplastic or thermosetting resin forexample. Exemplary resins include epoxy, polyimide, polyamide,bismaleimide, polyester, vinyl ester, phenolic, polyetheretherketone(PEEK), polyetherketone (PEK), polyphenylene sulfide (PPS), and thelike.

The fibers of tubes 403 may be oriented in one or more directions andmay be woven or unwoven. It should be appreciated that tube 307 mayalternatively only include fibers arranged in a single direction, suchas a uniaxial or helical fiber configurations. In yet anotherembodiment, a first ply comprises fibers and a second ply comprisesfibers, such that the second ply is laid-up over the first ply.

Referring now also to FIG. 6, a method 601 of manufacturing a compositecore, such as composite core 401, is schematically illustrated. Method601 can include a step 603 of configuring a plurality of mandrels. Astep 605 can include wrapping a composite material around each mandrel.A step 607 can include assembling the wrapped mandrels. A step 609 caninclude curing the composite material to form a cured core member. Astep 611 can include cooling the mandrels and removing the mandrels fromthe cured core member. Each step of method 601 is described in furtherdetail herein.

Referring to FIG. 21, a cross-sectional view through a mandrel 701 isillustrated. Step 603 includes configuring a plurality of mandrels. Inthe illustrated embodiment, mandrel 701 is a metallic mandrel, such analuminum material. Mandrel 701 is configured having a material with arelatively low coefficient of thermal expansion (CTE). In theillustrated embodiment, mandrel 701 is preferably cured in a tool thatutilizes a bladder or other device to apply pressure from the exterior.However, it should be appreciated that method 701 can also be configuredwith a material having a desired amount of CTE so that curing pressureis derived from a thermal expansion of the mandrels within a confiningtool.

Mandrel 701 may be configured with a hollow portion 703 extendingthrough the centerline length of mandrel 701, forming a body portion 705between hollow portion 701 and outer surface 707. Mandrel 701 isconfigured so that during the curing process of the composite core 401,the temperature of each mandrel 701 is increased such that body portion705 volumetrically expands uniformly both in an inward direction and anoutward direction, until outer surface 707 is bounded by its nearestneighbor mandrel, at which point the pressure exerted by mandrel 701 onits nearest neighbor mandrel remains relatively constant, and thethermal expansion of body portion 705 continues primarily in inwarddirection. The degree of thermal expansion each mandrel 701 is dependentupon the CTE of the material of each mandrel 701. The geometry ofmandrel 701 can be selected to tailor the physical properties of mandrel701 and the resultant composite core 401. Further, the geometry ofmandrel 701 can be selected to tailor the strength/stiffness of themandrel 701. Further, the wall thickness of body portion 705, as well asthe geometry of hollow portion 703, can be selectively controlled toproduce a desired thermal expansion profile. For example, a mandrelhaving a smaller hollow portion 703 would provide a higher externalpressure than mandrel 701. In the illustrated embodiment, hollow portion703 is of a cylindrical shape; however, it should be appreciated thatother embodiments may have non-cylindrical shapes.

Each mandrel 701 is configured with a hollow portion 703 which allowshot air to be ducted therethrough during the cure cycle, as discussedfurther herein. However, it should be appreciated that an alternativeembodiment of mandrel 701 does not include a hollow portion 703. Itshould be appreciated that mandrel 701 is merely illustrative of a widevariety of mandrel configurations contemplated. Even though the exteriorshape of the mandrels are illustrated as hexagonal, the presentdisclosure includes mandrels having other exterior shapes, such assquare, rectangular, triangular, to name a few examples. Further, itshould be appreciated that the hollow portion within the mandrels can beany variety of shape, or shapes. The exact shape of the hollow portionis implementation specific.

In one example embodiment, a Teflon material, or other bond resistantmaterial or coating, can be used to prevent the composite material frombonding to the exterior surface of mandrel 701 during the cure cycle. Assuch, each mandrel 701 can include a layer 709 of the bond resistantmaterial adjacent to the outer surface 707 of each mandrel 701.

Referring again to FIG. 6, step 605 includes wrapping composite materialaround each mandrel, such as mandrel 701. The exact method of wrappingor otherwise depositing the uncured composite material on the exteriorsurface of each mandrel is implementation specific. In the preferredembodiment, one or more steps of method 601 are performed by anautomated system; however, it should be appreciated that any of thesteps can be performed manually.

Referring also to FIG. 7, a system 801 for at least partially performingone or more steps of method 601 is illustrated. Further, system 801 isparticularly well suited for performed steps 605 and 607. Step 605includes wrapping composite material around each mandrel. Step 607includes assembling the wrapped mandrels. Each of steps 605 and 607, aswell as system 801, are further described herein.

System 801 can include a hopper 803 configured to house a plurality ofmandrels 701. Each mandrel 701 can be selectively deployed and capturedby a winding jig 805. For example, each mandrel 701 can be released ontoa conveyor 807 and picked up by the arms of winding jig 805.

Referring also to FIG. 8, an embodiment of winding jig 805 isillustrated. Winding jig 805 is configured to position and retainmandrel 701 for the depositing of composite material thereon. It shouldbe appreciated that winding jig 805 can take on a variety ofimplementation specific configurations. In one embodiment, winding jig805 can include a driver 809 and a support member 811. Adapters 813 aand 813 b are operably associated with driver 809 and support member811, respectively. A coupling 815 a is positioned between driver 809 anda first end portion of mandrel 701. Similarly, a coupling 815 b ispositioned between support member 811 and a second end portion ofmandrel 701.

Winding jig 805 is configured to operably secure mandrel 701 betweencouplings 815 a and 815 b. Couplings 815 a and 815 b have similargeometry to that of mandrel 701. Further, winding jig 805 is configuredsuch that the geometry of couplings 815 a and 815 b are aligned withmandrel 701 during the composite material winding process. In theillustrated embodiment, driver 809 is configured to drive the rotationof adapters 813 a and 813 b, couplings 815 a and 815 b, and mandrel,while support member 811 is configured to provide freewheeling support.In an alternative embodiment, mandrel 701 and couplings 815 a and 815 bare held stationary while a device operates to place the compositematerial about the mandrel and couplings 815 a and 815 b, as discussedfurther herein. It should be appreciated that winding jig 805 is merelyillustrative of a fixture that can be used to facilitate the depositingof composite material onto mandrel 701 in step 605 of method 601.

Referring also to FIG. 9A, one non-limiting example embodiment ofwinding jig 805 for performing at least step 605 of method 601 isillustrated. Winding jig 805 is mounted to a platform 817 that can betranslated along a prescribed path. A first end portion of slit 819 canbe secured to a mount 821 that is secured to platform 817. Slit 819 ispositioned through an opening 823 in coupling 815 b. A second endportion of slit 819 can remain part of a roll 827 of composite material.In one embodiment, a plurality of cutting members cut roll 827 ofcomposite material into a plurality of slits 819 at prescribed widths,each slit 819 being fed to different winding jigs 805. Platform 817 isbiased in direction 825 by a constant tension member such that slit 819is held in tension. Mount 821 and roll 817 are positioned so that slit819 is oriented at a desired angle relative to mandrel 701. In theillustrated embodiment, the desired angle of slit 819 is 45 degrees;however, slit 819 can be oriented at any desired angle.

Referring also to FIG. 9B, the operation of winding jig 805 isillustrated. Driver 809 is operated so as to cause mandrel 701 torotate, which causes slit 819 to wrap around mandrel 701. As slit 819wraps around mandrel 701, platform 817 is pulled toward roll 817 indirection 829 while the wrap angle is maintained.

Referring also to FIG. 10, another example embodiment of a winding jig1005 for wrapping composite material on each mandrel 701 in step 605 isillustrated. Winding jig 1005 is substantially similar to winding jig805; however, winding jig 1005 is configured so that mandrel 701 is heldstationary while a material placement head 1001 moves around mandrel701, as well as translates along an axis of mandrel 701, such as indirections 1007 and 1009, respectively. Material placement head 1001 isconfigured to feed composite material while moving in a prescribed path.In such an embodiment, slit 819 can be secured at a stationary mount1003 so that slit 819 can be placed in tension by material placementhead 1001 as slit 819 is wrapped around mandrel 701.

Referring also to FIG. 11, another example embodiment of a winding jig1105 for wrapping composite material on each mandrel 701 in step 605 isillustrated. Winding jig 1105 is substantially similar to winding jig1005; however, winding jig 1105 is configured so that mandrel 701 isrotated in a direction 1107 while material placement head 1001translates along an axis of mandrel 701 corresponding with direction1009. In such an embodiment, slit 819 can be secured to coupling 815 a,for example, so that tension can be formed in slit 819 as materialplacement head 1001 translates and mandrel 701 rotates.

In another example embodiment, the winding jig is configured totranslate along a direction corresponding with the axis of mandrel 701while material placement head 1001 rotates but does not translate.

It should be appreciated that the winding jig can be configured in anycombination of the configurations described herein. For example, mandrel701 can rotate in a first rotational direction while material placementhead 1001 rotates around mandrel 701 in an opposite direction to that ofthe first rotational direction. Further, either mandrel 701 cantranslate along its axis or the material placement head can translate ina direction corresponding to the mandrel axis, or any combinationthereof.

It should be appreciated that the exact system and method for depositingraw composite material on mandrel 701 can be dependent at least upon thematerial form of the raw composite material.

Referring also to FIG. 12, one technique of wrapping uncured compositematerial around mandrel 701 utilizes a filament winding process. Acontinuous, resin-impregnated fiber 1401, extending from a filamentwinding machine 1403, is wound about mandrel 701. The resin can beeither a thermosetting or thermoplastic resin and becomes the polymericmatrix of tube 403 upon curing. The material placement process may beconducted in a variety of processes; for example, mandrel 701 can moveaxially while a spool of fiber 1401 rotates around the mandrel 701, asindicated by an arrow 1407. Alternatively, a spool or a plurality ofspools of material could rotate around mandrel 701. Relative motion ofthe material dispensing mechanism to mandrel 701 is inferred. As fiber1401 is wound onto mandrel 701 by filament winding machine 1403, ahelical shaped pattern is formed. One or more plies 1409 of fiber 1401,in desired orientations with respect to mandrel 701, are wound ontomandrel 701 to form the basic geometry of tube 403. The angle of whichfiber 1401 is wound about mandrel 701 may vary along the length of themandrel 701 in order to customize the strength of core 401. For example,the angle of the fiber 1401 may be dynamically changed during thematerial placement process in order to customize a compressive strengthof the core. Note that, in the illustrated embodiment, mandrel 701exhibits a size and shape corresponding to cell 405 (see FIG. 4 or 5).It should be further noted; however, that the present disclosure is notlimited to the particular illustrated configurations of filament windingmachine 1403 or mandrel 701. Mandrel 701 and the one or more plies 1409that have been filament wound onto mandrel 701 are subsequentlyassembled with other mandrels and plies, as will be discussed in greaterdetail herein, to form core 401 (shown in FIG. 4). It should further beappreciated that upon cutting of plies 1409 and the mandrel 701, thematerial may have a tendency to un-wind. A band of material, potentiallyadhesive or fibrous, may be used to keep fiber 1401 from unraveling uponcutting of the plies 1409 and the mandrel 701. An adhesive material withunidirectional fibers could be used to band the fiber 1401 on mandrel701. Further, the band can be selectively located and used to provideextra support for a subsequent post processing procedure of the core,such as a machining process.

In yet another example technique of performing step 605 of method 601,shown in FIG. 13, wrapping uncured composite material around mandrel 701is performed using a fiber placement process. A continuous,resin-impregnated tow 1301 (only one labeled for clarity) ofapproximately, but not limited to, 1000 fibers is applied to a mandrel701 by a fiber placement machine 1305. It should be appreciated that tow1301 may also be portions of a full tow; for example, tow 1301 may be ahalf tow of 500 fibers. In lieu of a tow 1301, a tape of fibers, cut toa prescribed width, may be used. A pre-cut tape of fibers may bereferred to as a “slit-tape.” A slit-tape allows the user to moreclosely control the width dimension, as compared to a tow of fibers.Exemplary prescribed widths of slit-tape include ⅛″ and ¼″, to name afew. The resin can be a thermosetting or thermoplastic resin, to nametwo examples, and becomes the polymeric matrix of tube 403 upon curing.During the fiber placement process, mandrel 701 can move axially whiletow 1301 rotates around the mandrel 701, as indicated by an arrow 1307.As tow 1301 is applied to mandrel 701 by fiber placement machine 1305, ahelical shaped pattern is formed. One or more plies 1309 of tow 1301, indesired orientations with respect to mandrel 701, are wound onto mandrel701. In one embodiment, one or more non-helical plies layers may beassembled on mandrel 701 to customize mechanical properties in certaindirections. It should be appreciated that more than one tow 1301 orslit-tape of different materials may be used. Note that, in theillustrated embodiment, mandrel 1303 exhibits a size and shapecorresponding to cell 405 (see FIG. 4 or 5). It should be further noted,however, that the present disclosure is not limited to the particularillustrated configurations of fiber placement machine 1305 or mandrel701. Mandrel 701 and the one or more plies 1309 that have been fiberplaced onto mandrel 701 are subsequently assembled with other mandrelsand plies, as will be discussed in greater detail below, to form core401 (shown in FIG. 4).

Referring now also to FIGS. 14-16, one example embodiment of step 605includes wrapping mandrel 701 with a broadgood form of slit 819 in sucha procedure that results in solid passageway or “closed cell” geometry.Namely, the broadgood form of slit 819 has a width W1 that is selectedto prevent a gap or space in the slit 819 after slit 819 is wrappedaround mandrel 701. Further, as slit 819 is wrapped around mandrel 701,a continuous seam 831 is formed; however, seam 831 is not a gap or spacein the material, rather seam 831 represents an abutment of helicallywrapped material, such as slit 819, which is an example of a customizedwidth broadgood composite material. In contrast, the wrapping of amandrel with composite material that produces a gap or space in thematerial, or an “open cell” geometry, as described with regard to FIGS.12 and 13, can have undesirable attributes in certain implementations.For example, the “open cell” embodiment may be limited by the widths ofthe tows or slits having to be consistent, resulting in having only afixed whole number of tows for a given spacing and angle, and the gapshaving to be a uniform width. The result is only having a fixed wholenumber of materials for a given spacing and angle. The angle with whichthe tow or slit is wrapped cannot be varied infinitely and still retaina specific tow or slit width and spacing. Furthermore, an “open cell”geometry core can be undesirable in some panel implementations becauseof insufficient bond surface at the core/skin interface. Further, for agiven mandrel geometry there are a limited number of tow or slit widthand gap combinations that will satisfy construction of the core tube fora given wrap angle.

Referring in particular to FIGS. 15 and 16, the orientation fibers 1501of slit 819 is implementation specific. In the embodiment illustrated inFIG. 15, fibers 1501 are unidirectional such that all the fibers extendin a direction corresponding with the length of the slit 819. In theembodiment illustrated in FIG. 16, fibers 1501 are multidirectional soas to form a fabric configuration.

Still referring to FIGS. 14-16, a nominal width W1 of slit 819 can becalculated by multiplying the circumference of the exterior surface ofmandrel 701 by the cosine of the wrap angle A1. One major advantage ofusing slit 819 to wrap mandrel 701 without material gaps is that theangle A1 can be customized for the core implementation while simplyadjusting for the width W1 of slit 819. Furthermore, the slit 819 can becut off from a much wider roll of bulk raw material, such that thecustomization of width W1 can be simply a matter of adjusting thecutting tool to provide the implementation specific width. Customizingthe angle A1 allows a user to tailor the physical properties of the coreby orienting the fibers 1501 in a direction to produce said physicalproperties. Referring briefly to FIG. 17, an example cutting tool 1701is illustrated. Cutting tool 1701 can have a plurality of cuttingmembers 1703, such as blades, that can be oriented to cut slits 819 atprescribed widths from a raw material roll 1705. Each slit 819 can becommunicated to a winding jig 805, as discussed further herein. Cuttingtool 1701 is especially well suited for cutting slits 819 havingunidirectional fibers such that cutting members 1703 cut the rawmaterial along between adjacent fibers. In contrast, a cutting toolhaving a male/female press cutting members may be better suited forcutting slits 819 having multidirectional fibers.

Still referring to FIGS. 14-16, the “closed cell” geometry core producedby wrapping broadgood composite material in step 605 of method 601enables the use of much thinner and lighter composite material, therebyproducing a core with very low density. Further, the “closed cell”geometry core can have significantly higher stiffness and strength thanis achievable with “open cell” geometry core. Furthermore, “closed cell”geometry core is fully tailorable.

In another embodiment of step 605 of method 601, mandrel 701 is wrappedmultiple times to produce multiple layers of composite material layers.In such an embodiment, the fiber orientation, wrap angle, and/orwrapping direction can be varied to produce tailored mechanical andphysical properties.

In some situations it may be desirable to provide ventilation and/ordrainage in the composite core, such as in a wing member of an aircraftthat also functions as a fuel tank. In such an embodiment, step 605 ofmethod 601 can also include creating perforations in the raw material orslit 819. The perforations can be created by any variety of methods; onemethod can be running the raw material or slit 819 over a spiked wheelor spiked roller support, for example.

Referring again to FIGS. 6 and 7, step 607 of method 601 includesassembling the wrapped mandrels. Step 607 can further include assemblingand inserting the wrapped mandrels in a tool or other fixture. The exactconfiguration of the tool is implementation specific. Referring now alsoto FIGS. 18-20, an example of a tool 1201 is illustrated. Tool 1201 isconfigured to produce a hexagonal shaped core member; however, tool 1201can be configured to provide any desirable shape. For example,alternative shapes of tool 1201 can be configured to produce circular,square, rectangular, or even part customized core shapes. In theillustrated embodiment, the plurality of mandrels 701 having wrappedcomposite material are assembled onto partial tool members 1203 a-1203 fin a pyramid shape. In one embodiment, system 801 is configured toautomate the assembly and stacking of wrapped mandrels, as shown in FIG.7. In another embodiment, the assembly and stacking of wrapped mandrelscan be performed manually. Each partial tool member 1203 a-1203 f caninclude apertures 1205 to control and tailor any thermal expansion ofthe partial tool member 1203 a-1203 f during the cure process. In oneembodiment, each partial tool member 1203 a-1203 f is stacked with sevenlevels of wrapped mandrels. Upon assembling each partial tool member1203 a-1203 f and their wrapped mandrels, one additional wrapped mandrel1205 is located in the center. However, it should be appreciated thateach partial tool member 1203 a-1203 f may be stacked with wrappedmandrels and assembled in a variety of ways.

In one example embodiment, tool 1201 includes a bladder 1207 that isconfigured to inflate to provide a prescribed inward pressure upon theassembly of wrapped mandrels 701. However, it should be appreciated thatthe present disclosure contemplates other methods of providing pressureto the composite material wrapped around each mandrel 701 during thecuring process, such as mechanical pressure generating devices.

In another embodiment, curing pressure can be generated by the thermalexpansion of the mandrels 701. In such an embodiment, tool 1201 caninclude a rigid constraining structure in lieu of bladder 1207. Theheating of the mandrels 701 causes thermal expansion, which generatespressure at the composite material between mandrels 701.

Tool 1201 can include a blower 1209 for generating an airflow 1211 andevenly distributing the airflow through the interiors of the pluralityof mandrels 701. In an alternative embodiment, a fluid, such as an oil,is circulated through the interiors of the plurality of mandrels 701.Step 609 can include heating the wrapped mandrels within tool 1201 for aprescribed duration in accordance with the cure requirement of thecomposite system. An oven can be used to generate that requisite heat,for example. Airflow 1211 can improve the heating rate and heatdistribution to the composite material wrapped around each mandrel 701,as such; it is particularly desirable to have an interior openingthrough each mandrel 701 that is sized to accommodate a prescribedamount of airflow. Bladder 1207 can be controlled by a controller 1213so as to tailor the amount and timing of pressure exerted at the cellwalls of composite material between mandrels 701 within tool 1201.

Referring again to FIG. 6, step 609 of method 601 includes curing thecomposite material wrapped around the mandrels 701 to form the curedcomposite core 401. As discussed further above, the uncured compositematerial around each mandrel 701 is cured by subjecting the assembly tothe requisite temperature and pressure. As discussed above, thetemperature and rate of temperature change of the composite material canbe controlled in part by blowing hot air through the interior ofmandrels 701. During the curing process of step 609, the temperature andpressure exerted upon the composite material is implementation specific.Bladder 1207 can be controlled by controller 1213 so as to tailor theamount and timing of pressure exerted at the cell walls of compositematerial between mandrels 701 within tool 1201. For example, bladder1207 can be controlled by controller 1213 to change the amount ofpressure during a viscosity change of the resin in the compositematerial.

After the cure cycle is complete, a composite core 401 is achieved asthe uncured composite material around each mandrel 701 becomes rigidlybonded to each adjacent tube 403. It should be noted that composite core401 that is formed by wrapping mandrels 701 with unidirectional fiberslits 819 at a prescribed angle produces composite core 401 that hascross-linked fibers at the cell walls. For example, multiple mandrels701 wrapped at a wrap angle of +45 degrees with slits 819 havingunidirectional fibers will produce cured composite core 401 with cellwalls having two plies of fibers at 90 degrees to each other. Thisunique result of the method and system of the present disclosureproduces a very lightweight and strong composite core 401.

Still referring to FIG. 6, step 611 of method 601 includes coolingmandrels 701 and removing mandrels 701 from the composite core 401.

The systems and methods disclosed herein include one or more of thefollowing advantages. The method of the present disclosure allows forthe efficient production of composite core, which can reduce the cost ofthe composite core. Further, wrapping mandrels with unidirectional slitsprovides tailorability of the composite core. Further, the method ofcuring composite core results in a high quality composite core.

The particular embodiments disclosed herein are illustrative only, asthe system and method may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Modifications, additions, or omissionsmay be made to the system described herein without departing from thescope of the invention. The components of the system may be integratedor separated. Moreover, the operations of the system may be performed bymore, fewer, or other components.

Furthermore, no limitations are intended to the details of constructionor design herein shown, other than as described in the claims below. Itis therefore evident that the particular embodiments disclosed above maybe altered or modified and all such variations are considered within thescope and spirit of the disclosure. Accordingly, the protection soughtherein is as set forth in the claims below.

To aid the Patent Office, and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims to invokeparagraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereofunless the words “means for” or “step for” are explicitly used in theparticular claim.

The invention claimed is:
 1. A method of wrapping a mandrel with acomposite material, the method comprising: securing the mandrel and afirst coupling with a winding jig such that the first coupling islocated adjacent to a first end of the mandrel while sharing a centralaxis with the mandrel, the mandrel and the first coupling each having asame hexagonal shape and hexagonal circumference, wherein the mandrelhas a hollow interior extending along a length of the mandrel to providea fluid passage for heating of the mandrel during a curing process;orienting the composite material at a wrap angle to the mandrel and thefirst coupling and depositing the composite material around thehexagonal circumference of the mandrel and the first coupling startingfrom the first coupling, such that the composite material completelycovers the hexagonal circumference of the first end of the mandrel. 2.The method according to claim 1, wherein the composite material is aslit of composite material, the slit having a prescribed width.
 3. Themethod according to claim 2, wherein the step of depositing thecomposite material around the hexagonal circumference of the mandrelincludes wrapping the slit of composite material at the wrap angle thatprevents formation of a gap in the slit of composite material as theslit is wrapped around the mandrel.
 4. The method according to claim 1,further comprising: cutting the composite material to a prescribed widthso that the step of depositing the composite material around thecircumference of the mandrel produces a helical seam.
 5. The methodaccording to claim 1, wherein the step of depositing the compositematerial around the hexagonal circumference of the mandrel includesrotating the mandrel on the winding jig while maintaining the wrap angleof the composite material to the mandrel.
 6. The method according toclaim 5, wherein the maintaining the wrap angle of the compositematerial to the mandrel includes translating the winding jig toward asource of the composite material.
 7. The method according to claim 1,wherein the step of depositing the composite material around thehexagonal circumference of the mandrel includes rotating a material feedhead around the mandrel.
 8. The method according to claim 7, wherein thestep of depositing the composite material around the hexagonalcircumference of the mandrel further includes translating the materialfeed head in a direction corresponding with the central axis of themandrel.
 9. The method according to claim 7, wherein the step ofdepositing the composite material around the circumference of themandrel further includes translating the mandrel in a first directioncorresponding with the central axis of the mandrel.
 10. The methodaccording to claim 9, wherein the step of depositing the compositematerial around the hexagonal circumference of the mandrel furtherincludes translating the material feed head in a second directionopposing the first direction.
 11. A method of manufacturing a compositecore for use in a structural assembly, the method comprising: wrapping ahexagonal mandrel in a mandrel wrapping process comprising: securing thehexagonal mandrel and a coupling in a winding jig, such that thecoupling is located adjacent to a first end of the hexagonal mandrelwhile sharing a central axis with the hexagonal mandrel, the couplinghaving the same hexagonal shape and hexagonal circumference as thehexagonal mandrel, the mandrel having a hollow interior extending alonga length of the mandrel to provide a fluid passage for heating of themandrel during a curing process; orienting a composite material at awrap angle to the mandrel; and depositing the composite material arounda circumference of the hexagonal mandrel; assembling a plurality ofwrapped mandrels adjacently in a tool; and applying a pressure to thecomposite material during a curing cycle.
 12. The method according toclaim 11, wherein the composite material is a slit of compositematerial, the slit having a prescribed width.
 13. The method accordingto claim 12, wherein the step of depositing the composite materialaround the hexagonal circumference of the hexagonal mandrel includeswrapping the slit of composite material at the wrap angle so as toprevent formation of a gap in the slit of composite material as the slitis wrapped around the hexagonal mandrel.
 14. The method according toclaim 11, further comprising: cutting a slit of the composite materialto a prescribed width so that the step of depositing the compositematerial around the circumference of the mandrel produces a helicalseam.
 15. The method according to claim 11, wherein the step ofdepositing the composite material around the hexagonal circumference ofthe hexagonal mandrel includes rotating the hexagonal mandrel on thewinding jig while maintaining the wrap angle of the composite materialto the hexagonal mandrel.
 16. The method according to claim 15, whereinthe step of maintaining the wrap angle of the composite material to thehexagonal mandrel includes translating the winding jig toward a sourceof the composite material.
 17. The method according to claim 11, whereinthe step of depositing the composite material around the hexagonalcircumference of the hexagonal mandrel includes rotating a material feedhead around the hexagonal mandrel.
 18. The method according to claim 17,wherein the step of depositing the composite material around thehexagonal circumference of the hexagonal mandrel further includestranslating the material feed head in a direction corresponding with thecentral axis of the hexagonal mandrel.
 19. The method according to claim17, wherein the step of depositing the composite material around thehexagonal circumference of the hexagonal mandrel further includestranslating the hexagonal mandrel along the central axis.